Development of root biomass in an Eucalyptus globulus plantation under different water and nutrient regimes

Abstract

The distribution along the soil profile of Eucalyptus globulus root biomass was followed in a plantation in central Portugal at 1, 2 and 6 years after planting, using an excavation technique. The experimental design consisted of a control (C) and 3 treatments: application of solid fertilizers twice a year (F), irrigation without the application of fertilizers (I) and irrigation combined with liquid fertilizers (IL). Below-and above-ground biomass decreased as follows: IL>I>F>C. So, water stress limited growth more severely than nutrient stress. The roots rapidly colonized the top soil volume (0-20 cm depth) during the first year after planting. Fine root biomass 6 years after planting was 2.2, 1.8 and 1.6 times higher in IL treatment than it was respectively in control, and in F and I treatments. The distribution of fine roots along the soil profile 6 years after planting was more even in IL compared to the other treatments. However, fine roots in the top soil were more concentrated along the tree rows in the irrigated treatments than in the others. The proportion of below-ground biomass relative to the total tree biomass and the root/shoot ratio were higher in C than in the treatments at early growth stages. This pattern was not so clear 6 years after planting, due to the increased proportion of the tap root relative to total biomass, especially in the IL treatment.

Spatial and temporal patterns of root distribution in developing stands of four woody crop species grown with drip irrigation and fertilization

“…Rooting density declined with distance from the drip tube in all genotypes, but rooting density did not decline with distance from tree stems along the drip tubes (x). Drip tubes used for delivery of water and nutrient treatments consistently influence fine-root biomass and density in other woody species including Eucalyptus globulus Labill., l7zuja occidentalis L. and Prunus armeniaca L. (Fabib et al 1995;Pronk et al 2002;Ruiz-Shnchez et al 2005). Use of drip tubes to supply water and fertilizer creates heterogeneous soil conditions.…”

“…These relative sample locations were selected to capture spatial heterogeneity in fine-root biomass that was expected to result fiom treatments supplied through the drip tube (cf. Burt and Styles 1994;Fabib et al 1995;Ponder et al 1984;Robinson 1994). In each of the 4 years, five different trees were randomly selected per plot and one of the five relative sample locations was randomly assigned to each.…”

“…One way to evaluate the response to soil heterogeneity is to overlay systematic heterogeneity within a model forest and generate predictable patterns of resource distribution. Drip imgation tubes used in intensive forest management operations create such a systematic pattern of resource heterogeneity (Fabib et al 1995;F'ronk et al 2002;Ruiz-Shnchez et al 2005), which will aid in defining the relative magnitude of genetic versus environmental controls over root distribution.…”

Biomass expansion factors for Eucalyptus globulus stands in Portugal

“…The treatments were daily irrigation from April to October (I); broadcast application of a pelleted fertilizer twice a year (in March and October) (F); and daily irrigation combined with a simultaneous application of liquid fertilizer once a week during the dry season (FI). One and two years after planting, 24 trees (6 trees per treatment) were selected for root measurements from a group of trees randomly harvested for aboveground biomass measurements (Fabião et al, 1995). Six years after planting, only block 2 was available, and a tree with a diameter near the treatment mean was chosen from each plot, for a total of 4 trees (Fabião et al, 1995).…”

Mixed and Monospecific Stands of Eucalyptus and Black-Wattle. Ii - Fine Root Biomass Density

“…The opposite is expected in more productive sites, with more fertile soils, in which the root system would not need to extend as far to absorb the necessary volume of water and nutrients that are vital for metabolic activity. On evaluating the fine root system of Eucalyptus globulus, Fabião et al (1995) found that interference in root growth would be more accentuated in a situation of water stress than for nutrient shortage. Nambiar (1983) reported that other factors may be important in the distribution of forest species fine roots (e.g.…”